Ladder of the rail-rung type



July 6, 1965 c. D. DOSKER LADDER OF THE RAIL-HUNG TYPE Filed Sept. 3, 1965 m R K O S 1 l T O -5 4 Z. m D V w 6 k I N m m U E N R 1 0 C ATTORNEY United States Patent M 3,193,051 LADDER OF THE RAE-RUNG TYPE Cornelius D. Dosker, Louisville, Ky., assignor to Gamble Brothers, Inc., Louisville, Ky., a corporation of Kentucky Filed Sept. 3, H63, Ser. No. 306,014 2 Claims. (Cl. 18246) It is desirable to provide electrical linemen, such as those engaged in repairing and maintaining telephone lines, electrical transmission lines and the like, with electrically safe ladders, that is to say ladders which support the lineman in space and insulate him from the ground. One electrically safe type of ladder, which presently enjoys substantial use by electrical linemen, is made of wooden rails which are interconnected by metal rungs composed of aluminum or magnesium. This type of ladder has been highly satisfactory although relatively heavy in weight.

The present invention relates to an electrically safe type of ladder composed of wood rails and metal rungs and has for its principal object a substantial lessening in weight without a corresponding sacrifice in strength and safety.

Metal ladders are conventionally composed of metal rails and rungs. The metal rails of such ladders are conventionally made of general I-beam shape in cross section characterized by front and rear flanges interconnected by a planar web. While wooden rails are conventionally made rectangular in cross section, it is conceivable that they might be made of general I-beam shape in cross section so that each is characterized by front and rear flanges and a planar flange-interconnecting web.

Another important object of the present invention is to provide a structurally strong relatively rigid ladder of the electrically safe type having wood rails, which are substantially lighter in weight than corresponding wood rails of rectangular cross section, and which is substantially more rigid than a wood rail of I-beam shape in cross section which is composed of wood flanges interconnected by a planar wooden web.

The important objects of my invention may be achieved in an electrically safe ladder of the wooden rail and metal rung type by employing a tranversely-spaced pair of elongate rails of general I-beam shape in cross section wherein each rail comprises: (1) front and rear flanges spaced in the direction of the depth of the rail; (2) a flange-interconnecting web (a) which extends lengthwise in the direction of the length of the rail and widthwise from one flange to the other so as to present an outer side and an 'inner rung-receiving side, and (b) which undulates sinuously along its length so as to present a succession of crests and valleys on its rung-receiving side; and (3) a succession of rung-receiving blocks uniformly spaced along the length of the web, (a) each block being positioned in a web valley on the rung-receiving side of the web and fixedly secured to the rail.

A ladder made in accordance with my present invention is substantially lighter in weight than a conventional wood ladder of corresponding size which employs wood rails of solid rectangular cross section. It is substantially stronger and more rigid than a wood rail composed of front and rear wood flanges interconnected by a planar wood web and this gain in strength and rigidity is not significantly offset by any increase in either weight or cost.

The invention is illustrated in the accompanying drawing wherein:

FIG. 1 is a somewhat schematic, small-scaled, perspective view of a ladder made in accordance with my invention;

FIG. 2 is a broken sectional view taken along a line 3,193,051 Patented July 6, 1965 corresponding to line 2-2 of FIG. 1 but made on a larger scale;

FIG. 3 is a side elevation, on a much larger scale, of a part of one rail of the ladder, this part including one end portion and an adjacent intermediate portion, it being understood that the opposite end portion preferably duplicates the structure of the illustrated end portion and the remainder of the intermediate portion preferably repeats the structure of the illustrated intermediate portion a number of times depending upon the overall length of the rail;

FIG. 4 is a section taken along line 44 of FIG. 2;

FIG. 5 is a section taken along line 55 of FIG. 3; and

FIG. 6 is a section of a modified construction taken along a line corresponding to line 55 of FIG. 3.

Ladder 01'' FIG. 1

The ladder illustrated in FIG. 1 comprises: a transversely-spaced. pair of side rails 10; and a succession of rail-interconnecting rungs 11 uniformly spaced along the length of the rails and secured to both.

The rails 10 preferably are composed wholly of wood although it is conceivable that a sinuous web of wood or metal might find advantageous use in some ladders using either composite rails or all metal rails.

The rungs 11 are preferably composed of light-weight metal such as aluminum or magnesium but, while lightness in weight is desirable, the use of metal rungs is not essential. Since the rungs themselves play no special part in the present invention, it does not appear necessary to describe them any further other than to say that preferably they are made in the form of hollow metal tubes.

The dimensions of a rail-rung ladder, made in accordance with my invention, may vary widely. However, for the sake of clarity, it may be assumed that the drawing is based on a 12 long ladder of conventional width, having a rail 1%" wide and 2% deep from front to rear with /8 deep flanges spaced 1 /2" apart.

Rails 0 FIGS. 2-5

While a metal rail, or a composite rail such as one composed of wood and metal, may be constructed in accordance with the broader aspects of this invention, an all wood rail is preferred; hence, the description which follows hereinafter is limited thereto. An all wood rail, constructed in accordance with the present invention for use in a ladder of the rail and rung type, comprises: A. an elongate wood rail 10 of general I-beam shape in cross section essentially including (1) front and rear flanges and (2) a sinuous flange-interconnecting web and preferably including (3) a succession of rung-receiving blocks spaced along the length of the rail.

Flanges The front and rear flanges 13 preferably are identically constructed. Each flange 13 may be composed of solid wood but it preferably is composed of laminated wood. As illustrated, it comprises: an inner wood strip 14; and an outer wood strip 15 which is adhesively bonded to the outer face of the inner strip by any of the well known conventionally employed resinous or other wood bonding agents.

The inner strip 14, which may be laminated, is shown as a /8" deep solid wood strip 14 preferably but not necessarily composed of spruce, a strong wood of light weight.

The outer strip 15, which may be composed of solid wood, is shown as a A" deep laminated strip composed of three layers of veneer 16, 17, 18, which may be crossbanded. The use of hickory veneer is recommended.

wood, it is far more advantageous to construct it of laminated wood and it is therefore illustrated, as composed of three plies of maple yeneer, preferably cross-banded,

and preferably having an overall thickness ranging from 3/ to of'an inch. The web 20 extends sinuously along the length of the rail so that it presentsanxouter side and an in'nerrung-receiving side with concave surface curvatures centrally based on a 3 /8 radius. The

distances from the center of one crest on its rung-receiving side to the centers of the next valley and of the next crest on the same side approximate 3" and 6" respectively as shown. Thecenter of each crest intersects the flanges 13 at a point spaced approximately of an inch inwardly from the adjacent long edge of the flange. long marginal edge portion of the sinuous web may be secured to the adjacent flange 13 in any suitable manner. Preferably this is accomplished by having that marginal edge portion project into'a 71 inch deep groove 21in the flange 13 where it isbonded in place by any suitable wood bonding agent.

Rang-receiving blocks The rung-receiving blocks comprise: a succession of intermediate blocks uniformly spaced along the length of the web; and a pair of terminal blocks, one at each 7 end of the -web. 7 composed of metal, plastic orwood, either solid or laminated. I

As shown each intermediate block 23 is composed. of

solid wood. It has a flatru-ng-rceiving face, which preferably is flush with the corresponding face of the adjacent front andrear flanges 13. It also has a front-to-rear spacing of the flanges 13. so that the front and rear faces of the block 23 will fit against the adjacent faces of the front and rear flanges 13 with suificient tight-nessto insure a good adhesive bond.- Finally each intermediate block :23 base, on the sinuous web side, a curved face shaped to conform to the valley of the sinuous Webjand toabut snugly against its'concave surface to insure a strong adhesive bond. Each intermediate block 23 is approximately '3" long. In a 12' ladder, nine such bloclgs'are spaced center-to-center at 1 2 intervals along the length of the sinuous web beginning with the'second concave pocket or valley in the rung-receiving side of the web and'ending with the'nexb to last valley.

While each terminal block 25,'at each end of the web, preferably is composed of Wood and while it'may be laminated, it is shown as composed of solid wood. Each terminal block 25 fills the front-to=rear. space between the front and rear flanges from the adjacent end of the web 20 to the adjacent end of the ladder. The web-end of block 25'is providedwith a /8" groove 26 to receive;

to 14) is laminated. Strip 14a may be composed of any suitable laminated wood, a multi-ply assembly of poplar veneer: or of any other suitable veneer fabricatedf romlightweight wood, i.e. wood having a density of about 30 pounds per cubic foot or less being recommended.

Each rungereceiving block may be Miscellaneous It will be readily recognized that an I-beam type of rail, which is provided with a sinuous web in accordance with my invention,is stronger than the same type of rail made with a planar web, For example, it, obviously, is harder to bend in any direction about its middle. It is also harder'to twist longitudinally about its centrally disposed long axis. .ThusfI have found that an I-beam type of planar web rail of one specific size and construction will twist about its centrally disposed long axis approximately one degree when subjected to a twisting torque ranging from .584 to .654 foot pounds whereas a comparable structure made in accordance with lmy invention requires approximately 1.33 foot pounds of torque per degree of twist. Each flange, in a rail made in accordance with my invention, obviously requires a greater eifort to twistit loosefromits long joint line'connection with the web than is the case with either flange in a planar web construction. The increased strengthand resistance of my rail is believed to be due to the-fact that, in "effect, it combines a long web with a series of cross webs.

Having described my invention, I claim: 1. A ladder ofgthe electrically-safe rail and rung type, comprising: i v I (A), a transversely-spaced pair. of elongate rails of general I-beam-shape in cross section, each rail being characterized by (1) elongate front and rear flanges composed of wood and spaced in the direction of the depth oftherail and (2) a flange-interconnecting web of wood (a) which extends lengthwise in the direction of the length of the rail and'widthwise from one flange to the other so as to present an outerside and an inner rung-receiving side, and

(b) which undulates sinuously along its length so as to present a succession of crests and valleyson its rung-receiving side, and

(3) a succession of rung-receiving blocks uniformly spaced along the length of the web,

(a) each block being positioned in a web valley on the rung-receiving side of the web and fixedly secured to the rail;]

(13.) a succession of rail-interconnecting. rungs uniformly spaced along the length of the rails and secured to both, l

' (1) each rung extending from a block in one rail to a corresponding block in the other rail. 2.The ladder of "claim 1 wherein; (A) each flange has an elongate web-receiving groove which undulates sinuously with the web; and

v (3) each block has a face shaped to conform to the web and abut; snugly against it.

2/3 1 France. 7/56 Great Britain.

702,945 751,882 7 HARRISON R. MOSELEY, Primary Examiner.

, CHARLES E. OCONNELL, REINALDO P. MACHA: I DO, Examiners. 

1. A LADDER OF THE ELECTRICALLY-SAFE RAIL AND RUNG TYPE, COMPRISING: (A) A TRANSVERSELY-SPACED PAIR OF ELONGATE RAILS OF GENERAL I-BEAM SHAPED IN CROSS SECTION, EACH RAIL BEING CHARACTERIZED BY (1) ELONGATE FRONT AND REAR FLANGE COMPOSED OF WOOD AND SPACED IN THE DIRECTION OF THE DEPTH OF THE RAIL AND (2) A FLANGE-INTERCONNECTING WEB OF WOOD (A) WHICH EXTENDS LENGTHWISE IN THE DIRECTION OF THE LENGTH OF THE RAIL AND WIDTHWISE FROM ONE FLANGE TO THE OTHER SO AS TO PRESENT AN OUTER SIDE AND AN INNER RUNG-RECEIVING SIDE, AND (B) WHICH UNDULATES SINUOUSLY ALONG ITS LENGTH SO AS TO PRESENT A SUCCESSION OF CRESTS AND VALLEYS ON ITS RUNG-RECEVING SIDE, AND 